Association of tumor genetics with outcomes in patients (pts) with PSMA-positive metastatic castration-resistant prostate cancer (mCRPC) treated with 177Lu-PSMA-617.

Background: ¹⁷⁷Lu-PSMA-617 is approved for the treatment (tx) of mCRPC. Though tx is associated with improved survival, not all pts experience a benefit. Acquired resistance is common and some pts have intrinsic resistance. There is a lack of data on genomic markers that could aid in selecting pts for tx. In this study, we aim to characterize molecular predictors of benefit to ¹⁷⁷Lu-PSMA-617. Methods: We used the retrospective Prostate Cancer Precision Medicine Multi-Institutional Collaborative Effort (PROMISE) clinical-genomic database (n=2100). The primary endpoint was to investigate the association of genomic alterations with a ≥50% PSA decline (PSA50) from baseline following ¹⁷⁷Lu-PSMA-617. Associations were assessed using Wald-chi square test and Cox regression in multivariable analysis. Secondary endpoints included clinical progression-free survival (PFS) and overall survival (OS). Results: We identified 115 pts with PSMA PET+ mCRPC treated with ¹⁷⁷Lu-PSMA-617 who had commercial genetic sequencing prior to tx (median age 72 yrs, 25% non-white). Median number of prior lines for mCRPC was 3 with 71 pts (62%) receiving >1 androgen receptor signaling inhibitor (ARSI) and 55 pts (48%) receiving >1 taxane; 11 pts (9%) received ARSI with ¹⁷⁷Lu-PSMA-617. Overall, the PSA50 was 49% with median OS and PFS of 14.0 and 7.6 months (mos), respectively. In pts with a PSA50, median OS and PFS were 22.6 and 11.6 mos, respectively, vs 11.2 and 5.6 mos for those without a PSA50. Genetic alterations associated with PSA50 are in the table. PSA50 was 48% in pts with (n=32) vs 49% in pts without DDR alterations (n=83). PSA50 was 44% in pts with tumor suppressor gene alterations (TSGa) (PTEN, p53, RB1) (n=68) vs 56% in pts without (n=47). Median PFS was 7.6 vs 7.3 mos for pts with and without any TSGa (p=0.90), and median OS was 12.2 mos vs 22.6 mos for pts with and without TSGa (p=0.004). Of the 43 pts with AR alterations, 8/15 (53%) with LBD mutations, 10/27 (37%) with AR amplification, and 0/1 with AR-V7 had a PSA50. FGFR, CDK12 and MYC alterations were enriched in individuals without a PSA50 (75-83%). Conclusions: We demonstrate that CDK12, MYC and FGFR alterations were associated with a lower PSA50 with ¹⁷⁷Lu-PSMA-617. Larger cohorts should be investigated for confirmation, as biomarkers to inform relative benefit of tx could be useful in prioritizing options for mCRPC. (Table presented.)

Duke Scholars

Author Andrew John Armstrong Medicine, Medical Oncology